Protective helmet



FIG. 1 is a right side view of a protective helmet showing the design;

FIG. 2 is a left side view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof.

The ornamental design which is claimed is shown in solid lines in the drawings. The broken lines of the drawings are for illustrative purposes only and form no part of the claimed design. 

CLAIM The ornamental design for a protective helmet, as shown and described. 